April 1, 2009

Wiring your brain at college – a new perspective on sleep

The transition to college requires students to become accustomed to many unfamiliar occurrences. Some of these transitions are expected, such as staying up late in order to finish a paper or to spend time with friends. Others are almost impossible to foresee, such as the strange scenarios that college hazing rituals bring about.

And then, there are some things that really aren’t that strange, but still take some time to get used to. For me, one of the most alien behaviors that I experienced was witnessing other people sleeping. Outside of college, when someone is tired, they go home and fall asleep in bed, away from the rest of the world. In college, people fall asleep everywhere: common rooms, the library, friend’s couches, etc. All of these places appear to be the perfect resting place for an exhausted student. Even if they do manage to make it back to their rooms, students often share the room with a roommate or two. And although there is nothing unfamiliar about sleeping, I often find myself surprised by how others sleep. Since coming to college, I have witnessed some pretty strange sleep occurrences. I have seen people sleeping in hallways, people talking in their sleep, and the most amusing by far, I have watched as people unknowingly twitch in their sleep.

Sleep is a vital part of all human life. Therefore, one of the biggest questions among scientists is; “why do we need sleep?” Currently there are many theories about the purpose of sleep. It is felt that sleep may have evolved to protect us, keeping us hidden from potential predators. Secondly, it is thought that sleep acts to repair damage that has occurred to the brain during the day. Researchers also believe that memories are solidified during sleep, transferring from short term to long term. Also, sleep is thought to be related to growth, as growth hormones are released during sleep (Myers, 2007).

Research suggests that sleeping may provide time for learning, especially among infants. As newborn infants are overwhelmed with new sights and sounds, sleep gives them time to explore and learn about themselves. This theory differs greatly from the original idea that twitches during REM sleep are caused by leaked signals slipping through to the motor cortex. Psychology professor Mark Blumberg feels that during sleep, the twitching of different parts of the body allows infants to determine what particular nerves do, and what response their activation will produce. By twitching, infants are able to “get to know” their bodies. Because people twitch most frequently during infancy, the study of infants may help to determine the purpose of twitching in all people, including college students.

Recent findings suggest that single neurons are responsible for individual muscles, so each neuronal connection must be learned individually in order for large-scale movements to occur (Petersson, Waldenström, Fåhraeus & Schouenborg, 2003). During sleep, infants are able to fire signals from individual neurons, allowing them to determine exactly what muscle is associated with that specific neuron.

Through this mechanism, infants are able to begin to understand their bodies. This knowledge does not only help them with coordination but also with responses to stimuli. In order to test this theory, Khazipov, et al (2004) set up situations in which infant rats received either the correct or the opposite feedback to their twitches during sleep. The “reverse-feedback” group received a puff of air on the left side of their tail when they twitched to the right, and a puff of air on the right side of their tail when they twitched to the left. After only a few hours of training it was found that the rats in the “reverse feedback” group exhibited strange responses when exposed to stimuli. For example, when the right side of their tails was touched with a hot laser, they often moved their tails towards instead of away from the heat source. These findings suggest that the twitches that occur during sleep are related to learning about the location and function of specific body parts. Humans appear to show a similar pattern, as it is found that the triggering of localized spindles that cause muscle twitches in in vivo rats are characteristic of the spindle bursts and movements of fetal humans. (Blumberg & Lucas, 1994)

You may be wondering, if these findings are correct, why do fully-grown humans still twitch in their sleep? Shouldn’t all of these connections be mapped by the time we reach adulthood? It is thought that the twitching that occurs during the REM sleep of adults’ acts to retain and refine the understanding of the body. As humans, and other sleeping organisms, age they twitch less in their sleep. This helps support the retention and refining theory, as less time is required to re-examine these neuronal connections, as it is to explore them for the first time.

So, the next time that you see an exhausted student sleeping in the library instead of studying, remember that they are still learning. With each involuntary twitch, they are reviewing and relearning all of the individual connections between neurons and muscles.

Like this:

Related

While I find the idea of twitching in our sleep as a form of learning interesting, I don’t think I necessarily agree with it. It may be a new theory that has some kinks that need to be worked out, but I know from personal experience that when I’m really sleep-deprived I tend to twitch a lot more, both in sleep and out of sleep, whereas when I am not sleep-deprived, my twitching frequency is a lot lower. These studies and my experience would then suggest to me that, for some reason, when I am sleep-deprived, my mind tests neurons much more frequently, as if it had forgotten how to use my muscles, and this seems implausible. For this reason I still buy into the idea that twitches are simply the motor cortex being activated by mistake — “leaked signals” as you put it.

As a side note, I wanted to expand on your idea that adults twitch in our sleep because it acts to retain and refine their understanding of their bodies. If the concept of the network activation model of learning is used, then this kind of twitching could be simply strengthening the links between “nodes”, allowing for faster and easier activations and therefore allowing for more coordinated movements of many muscles.

The relationship between mental review and sleep is something we probably all are familiar with, where there will be a period of improved recall just before we are ready to fall asleep. That seems to make sense that the neurons are entering some new state of activity, similar to what is expressed in the above post. Would they both make sense of the Sakadian [SIC] Cycles were responsible for both these behaviors?

As the author of this article mentioned early on in her post, scientists don’t really know the exact purpose of sleeping. I think we can all agree, however, that sleeping is necessary if an individual expects to approach the day feeling healthy and energized. I know that I am extremely unproductive if I have gotten less than five hours of sleep (unfortunately a common occurrence).
Scientific American recently published an article http://www.sciam.com/blog/60-second-science/post.cfm?id=can-a-good-nights-sleep-prevent-a-c-2009-01-12) about the link between hours of sleep and the likelihood of catching a cold. Apparently, people who get less than seven hours of sleep are three times more likely to catch a cold than those who get eight hours or more. Sleep deprivation can lead to a decreased number of killer T-cells and lower levels of interleukin-2, which is a protein that aids in the production of infenction-fighting cells. It is also not enough to just get sleep; if a person stays up all night tossing and turning, their immune system will suffer. I know from personal experience that simply staying in bed does not guarantee that I will well the next day. If I am in pain, overheated, or uncomfortable for any other reason the next morning is miserable.

Although I am not sure if I twitch while I sleep, I one time “sleep-walked” over to my closet and started getting dressed for school-at 3:00 AM. Recent research suggests that our environmental stimuli in waking-life reorganizes the brain’s structure of neurons in order for a person to learn and consolidate memories. Of course, all this restructuring occurs during sleep. Accordingly, sleep deprivation in rats reduces neurogensis, the ability of neurons to differentiate into specialized cells. In addition, REM sleep activates P-wave producing cells that stimulate areas of the brain that consolidate long term memory. Finally, the central nervous system functions differently in relation to the stages of sleep development in children: circadian rhythms, day-time sleep, and sleep-wake rhythm.

Here’s a response to the first comment. It would be interesting to find out whether these twitches happen during REM and/or nREM sleep. You claim that your body twitches more so when you’re sleep deprived, and one who is sleep deprived enters REM sleep more frequently. Because of this, I would guess that a majority of these twitches occur during REM sleep. However, we know that REM sleep is characterized by the absence of motor function with the exception of the eye muscles and the diaphragm. Perhaps the body is intentionally leaking signals to the motor cortex, not only to re-familiarize the neuron/muscle connections, but to reinforce learned movements from that day (whether it be handwritten class notes or walking down an unfamiliar path.) Just a thought.

I have never thought about why people twitch during their sleep, but I must admit that it is an interesting topic. Besides the refinement of understanding one’s body while we sleep, another proposal as to why we twitch is that as we drift into the unconscious of sleep we are relinquishing control over our motor functions. Some scientists believed that the twitches are stimulated by anxiety or some faint stimulus, like a noise. In one study, subjects were supposed to press a button when they heard a tone. After a while, the subjects eventually fell asleep. When the tone was sounded while the subjects were asleep, after a lag of a few seconds, they twitched, almost as if the semiconscious brain was trying to bring itself into action, (http://www.medicalscience.com/columns/read/82/why-do-we-twitch-while-falling-asleep) There are probably many hypotheses out there about why we twitch and maybe in the future we will understand if twitching has some sort of adaptive function.

As a student getting three or four hours of sleep on an average night, I find this post a little scary. I am also in a position to recognize and appreciate the many benefits of sleep. While the idea that sleep is necessary for maintaining muscle relationships is especially worrisome for a busy college student, it also provides a different perspective to the age-old adage about a good night’s sleep. On some level, it’s nice to attribute twitching in your sleep to such an easily explained circumstance, one that is both biologically beneficial and makes perfect sense. At the same time, sleep is still one of the most mysterious factors of life, biologically speaking, and most of the things our bodies and minds undergo during sleeping hours remain unknown.

Although the idea of muscle twitching as “relearning” neuron pathways is quite compelling, you have to take into account all of the other reasons why sleep is essential to the body. It is clear, from experience, that sleep has a hand in re-charging all different aspects of the human body – concentration, decision-making, immunity from sickness – all of these things are boosted by sleep and suffer as a result of a lack of sleep.

Response to Will Jobs’s:
I think the reason people twitch more when they are tired does necessarily have to deal with your body testing to see neural-muscle connections but more in the fact that your body is physically tired and you are unable to control it.

Besides of the brain repair mechanisms and psychological / neural reasonings for sleep, sleep is also a time when your body can physically recover from the day. Lot of the times your body uses up basic sugars that are stored in your muscles, resulting in fatigue since you do not have the energy to move. However, in sleep, your body can break down fats and other complex sugars stored in fat cells and the liver, replenishing the fuel needed for your body to run properly. Also I think that the the actual neural-muscular connections are fatigued from firing throughout the day. Thus, when you are tired, your muscles twitch because your body is less able to control the neural firings. I do not know if my reasoning is a correct or not but I am just basing it off of my biology knowledge.

I also think that sleep is heavily tied to an organisms circadian rhythms and basic metabolism. One’s circadian rhythm is their biological clock that affects one’s activity over a 24 hour period. This is affected by melatonin production that determines when one should be awake or asleep. In terms of metabolism, animals that are larger and that have a more herbivore diet, tend to require more sleep. This is probably because it takes a longer time to process the complex starches in plants and the fact that larger animals tend to have a slower metabolism and subsequently less energy.

I wrote my blog post on the reason for dreaming so I will just mention a bit of what I found. Dreaming occurs during REM sleep and has been linked to learning in various studies. One study, by Jay Dixit studied the effects of REM deprivation on rats. He found that the dream-deprived rats could not perform simple tasks related to survival skills such as hiding when placed out in the open. Even when they were given amphetamines, which should have counteracted their sleepiness, the rats still performed poorly, indicating that it was because they had not dreamed. Dixit proposed that dreams served as a sort of theater where one learns and remembers how to react in certain situations. Without dreaming, the rats did not have the necessary knowledge to perform well.

The more I think about it, the more sense this theory behind muscle twitching seems to make. In order to maintain homeostasis, the human body is constantly fixing itself, continuously making alterations to keep a stable inner environment. Cells degrade and regenerate, and in order to keep up with these slight changes, the brain needs to constantly re-explore the boundaries of the body it controls. So even when adults sleep, the fact that they twitch can be explained by the brains obligation to regularly pay attention to individual nerves and attached muscles.

Doing further research, I found an article on sleep myclonus (muscle twitching) from 1986, and it really made me realize how psychological theories have progressed. Éadaoin’s article supports the belief that these sleep twitches are a completely normal and advantageous aspect of human development and maintenance. However, the journal article from the 80’s examines this phenomenon in neonatals as a “benign syndrome” of an unknown disorder. They deem it not to be harmful to the infants nor inhibit regular growth, but they still characterize it as abnormal. I was amazed at how these theories about the same characteristic could vary so much, but it simultaneously reminded me that science has a long way to go before understanding the whole truth.

The author mentions that amongst other reasons that sleep is important is that growth hormones are released during sleep thus permitting not only growth but repair as well. Another important function of sleep that is still under investigation by researchers, is sleeps role in learning. It has been suggested that certain multilevel learning is done during the REM phase of sleep

As aforementioned in the post, sleep provides valuable time for learning, but not only for infants who are exploring and learning about themselves. In a 2006 study conducted by Walker and his colleagues, they administered a finger tapping task to various control groups. After learning the finger tapping sequence, the groups were tested at 12 and 24 hour intervals to measure performance on the task. The independent variable in the study was the timing of sleep; whether sleep was allowed between initially learning the sequence and the first test of performance and whether sleep was allowed between the first and second test of the sequence. In conclusion, both groups should significant improvement following sleep, but not following wakefulness, indicating that during sleep, the brain engages in miraculous feats. The study also indicated that following sleep, individuals showed improvements at problem points in the sequences, further supporting the assertion that the brain enables further learning while we sleep. Thus, deciding to go to sleep proves to be a valuable choice following a day of intense learning or memorization.